目录
（1）如果控制器的方法返回值写成void，执行会报404，默认JSP页面未找到
(3)还有一种方式：@RestController注解(=@Controller+@ResponseBody)
一、返回值分类
1.创建项目
2.pom.xml文件
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.qcby</groupId>
<artifactId>springMVC10</artifactId>
<version>1.0-SNAPSHOT</version>
<properties>
<maven.compiler.source>8</maven.compiler.source>
<maven.compiler.target>8</maven.compiler.target>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<!--版本锁定-->
<spring.version>5.0.2.RELEASE</spring.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-context</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-web</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-webmvc</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>servlet-api</artifactId>
<version>2.5</version>
<scope>provided</scope>
</dependency>
<dependency>
<groupId>javax.servlet.jsp</groupId>
<artifactId>jsp-api</artifactId>
<version>2.0</version>
<scope>provided</scope>
</dependency>
</dependencies>
</project>3.在web.xml文件里配置前端控制器和过滤器
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
version="4.0">
<!--配置解决中文乱码问题的过滤器-->
<filter>
<filter-name>characterEncodingFilter</filter-name>
<filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class>
<!--指定使用编码集-->
<init-param>
<param-name>encoding</param-name>
<param-value>UTF-8</param-value>
</init-param>
</filter>
<filter-mapping>
<filter-name>characterEncodingFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
<!--配置前端控制器-->
<servlet>
<servlet-name>dispatcherServlet</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
<!--加载springmvc.xml配置文件，配置的是Spring配置-->
<init-param>
<param-name>contextConfigLocation</param-name>
<param-value>classpath:spring-mvc.xml</param-value>
</init-param>
<!--配置启动加载-->
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>dispatcherServlet</servlet-name>
<url-pattern>/</url-pattern>
</servlet-mapping>
</web-app>4.spring-mvc.xml配置文件
<?xml version="1.0" encoding="UTF-8" ?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:aop="http://www.springframework.org/schema/aop"
xmlns:mvc="http://www.springframework.org/schema/mvc"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context.xsd
http://www.springframework.org/schema/aop
http://www.springframework.org/schema/aop/spring-aop.xsd
http://www.springframework.org/schema/mvc
http://www.springframework.org/schema/mvc/spring-mvc.xsd">
<!--配置扫描包-->
<context:component-scan base-package="com.qcby"></context:component-scan>
<!--配置视图解析器，进行页面的跳转-->
<bean id="viewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver">
<!--跳转的页面的路径-->
<property name="prefix" value="/pages/" />
<!--跳转页面的后缀名称-->
<property name="suffix" value=".jsp" />
</bean>
<!--让映射器、适配器和处理器生效(默认不配置也是可以的)-->
<mvc:annotation-driven/>
</beans>5.返回String
controller方法返回字符串可以指定逻辑视图的名称，根据视图解析器为物理视图的地址
@Controller
public class MyController {
//返回string
@RequestMapping("/sayHello")
public String sayHello(){
System.out.println("hello");
return "success";
}
}
6.返回void
在MyController里加了一个方法
//返回void
@RequestMapping("/sayHello2")
public void sayHello2(){
System.out.println("hello2..");
return;
}（1）如果控制器的方法返回值写成void，执行会报404，默认JSP页面未找到
（2）可以使用请求转发或重定向跳转到指定页面做出相应操作
@RequestMapping("/sayHello2")
//public void sayHello2(){
public void sayHello2(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException {
System.out.println("hello2...");
request.getRequestDispatcher("/WEB-INF/pages/success.jsp").forward(request,response);//①请求转发
//response.getWriter().print("hello2");//②
return;
}①的运行结果：
②的运行结果：
7.返回值是ModelAndView对象
在MyController里加了一个方法
（1）ModelAndView对象是Spring提供的一个对象，可以用来调整具体的JSP视图
（2）代码
@RequestMapping("/sayHello3")
public ModelAndView sayHello3(){
System.out.println("hello3...");
ModelAndView modelAndView=new ModelAndView();
modelAndView.addObject("msg","用户名或密码已经存在");
modelAndView.setViewName("success");
return modelAndView;
}
二、SpringMVC框架提供的转发和重定向
1.forward请求转发
在MyController里加了一个方法
controller方法返回String类型
//请求转发
@RequestMapping("/sayHello4")
public String sayHello4(){
System.out.println("hello4");
return "forward:/WEB-INF/pages/success.jsp";
}
2.redirect重定向
controller方法返回String类型
在MyController里加了一个方法
//重定向
@RequestMapping("/sayHello5")
public String sayHello5(){
System.out.println("hello5");
//return "redirect:http://www.itheima.com"; //(1)
return "redirect:/page/suc.jsp"; //(2)
}(1)的运行结果
（2）的运行结果
三、ResponseBody响应json数据！！！
json字符串和JavaBean对象相互转换的过程中，需要使用jaskson的jar包
1.引入依赖
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-databind</artifactId>
<version>2.9.0</version>
</dependency>
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-core</artifactId>
<version>2.9.0</version>
</dependency>
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-annotations</artifactId>
<version>2.9.0</version>
</dependency>2.DispatcherServlet会拦截到所有的资源，导致一个问题就是静态资源（img、css、js）也会被拦截到，从而不能被使用。解决问题就是需要配置静态资源不进行拦截，在springmvc.xml配置文件添加如下配置
标签配置不过滤
<!--配置静态资源不过滤
location元素表示webapp目录下的包下的所有文件
mapping元素表示以/static开头的所有请求路径，如/static/a 或者/static/a/b
-->
<mvc:resources location="/js/" mapping="/js/**"></mvc:resources><!--javascript-->
3.jsp代码
user.jsp
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>Controller方法的返回值</title>
<script src="js/jquery.min.js" type="text/javascript"></script>
<script>
$(function (){
$("#btn").click(function (){
//发送ajax请求
$.ajax({
type:"post",
url:"sayHello6",
contentType:"application/json;charset=utf-8",
data:'{"username":"zhang","age":"20"}',
dataType:"json",
success:function(d){
alert(d.username+"---"+d.age);
}
});
});
});
</script>
</head>
<body>
<h3>返回值是String</h3>
<a href="sayHello">返回String</a>
<h3>返回值是void</h3>
<a href="sayHello2">返回void</a>
<h3>返回值是ModelAndView</h3>
<a href="sayHello3">返回ModelAndView</a>
<h3>返回值是String</h3>
<a href="sayHello4">请求转发--返回String</a>
<h3>返回值是String</h3>
<a href="sayHello5">重定向--返回String</a>
<h3>异步的数据交互</h3>
<input type="button" value="ajax交互" id="btn" />
</body>
</html>4.实体类
package com.qcby.pojo;
import java.io.Serializable;
public class User implements Serializable {
private String username;
private Integer age;
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public Integer getAge() {
return age;
}
public void setAge(Integer age) {
this.age = age;
}
@Override
public String toString() {
return "User{" +
"username='" + username + '\'' +
", age=" + age +
'}';
}
}5.MyController
@RequestMapping("/sayHello6")
public @ResponseBody User sayHello6(@RequestBody User user){
System.out.println(user);
user.setUsername("hello");
user.setAge(40);
return user;
}这里有个@ResponseBody注解，所以在spring-mvc.xml中配置spring开启注解mvc的支持
6.运行
(1)
(2)加上response.getWriter().print("hello2")\
(3)
(4)
(5)
(6)
7.看MyController类中的save6()方法
@RequestMapping("/sayHello6")
public @ResponseBody User sayHello6(@RequestBody User user){
System.out.println(user);
user.setUsername("hello");
user.setAge(40);
return user;
}(1)@ResponseBody注解可以放上方法上面
@RequestMapping("/sayHello6")
@ResponseBody
public User sayHello6(@RequestBody User user){
System.out.println(user);
user.setUsername("hello");
user.setAge(40);
return user;
}结果是一样的
控制台：
(2)@ResponseBody注解还可以放在类上
这样返回的都是字符串(除了save2(它是response的那种写法)和save3(它是MpdelAndView对象，被翻译成json字符串以后还是一个对象，还是能解析成ModelAndView对象))
package com.qcby.controller;
import com.qcby.pojo.User;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.servlet.ModelAndView;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
@Controller
@ResponseBody
public class MyController {
//返回string
@RequestMapping("/sayHello")
public String sayHello(){
System.out.println("hello");
return "success";
}
//返回void
@RequestMapping("/sayHello2")
//public void sayHello2(){
public void sayHello2(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException {
System.out.println("hello2...");
//request.getRequestDispatcher("/WEB-INF/pages/success.jsp").forward(request,response);//请求转发
//response.sendRedirect("/WEB-INF/pages/success.jsp");//重定向这样写访问不到
response.getWriter().print("hello2");
return;
}
//返回ModelAndView
@RequestMapping("/sayHello3")
public ModelAndView sayHello3(){
System.out.println("hello3...");
ModelAndView modelAndView=new ModelAndView();
modelAndView.addObject("msg","用户名或密码已经存在");
modelAndView.setViewName("success");
return modelAndView;
}
//返回Model
@RequestMapping("/sayHello7")
public String sayHello7(Model model){
System.out.println("hello7...");
model.addAttribute("msg","用户名或密码已经存在");
return "success";
}
//请求转发,不走视图解析器了
@RequestMapping("/sayHello4")
public String sayHello4(){
System.out.println("hello4");
return "forward:/WEB-INF/pages/success.jsp";
}
//重定向，不走视图解析器了，重定向不可以是隐私目录
@RequestMapping("/sayHello5")
public String sayHello5(){
System.out.println("hello5");
//return "redirect:http://www.itheima.com";
return "redirect:/page/suc.jsp";
}
/*
* 异步的数据交互
* @ResponseBody这个注解要被扫描到，所以要在spring-mvc.xml中配置<mvc:annotation-driven />
* */
@RequestMapping("/sayHello6")
public User sayHello6(@RequestBody User user){
System.out.println(user);
user.setUsername("hello");
user.setAge(40);
return user;
}
}
点返回String:(是一个字符串，不是页面)
点返回void:
点返回ModelAndView:
点请求转发--返回String:
点重定向--返回String:
点ajax交互按钮：
(3)还有一种方式：@RestController注解(=@Controller+@ResponseBody)
package com.qcby.controller;
import com.qcby.pojo.User;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.servlet.ModelAndView;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
/*@Controller
@ResponseBody*/
@RestController
public class MyController {
//返回string
@RequestMapping("/sayHello")
public String sayHello(){
System.out.println("hello");
return "success";
}
//返回void
@RequestMapping("/sayHello2")
//public void sayHello2(){
public void sayHello2(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException {
System.out.println("hello2...");
//request.getRequestDispatcher("/WEB-INF/pages/success.jsp").forward(request,response);//请求转发
//response.sendRedirect("/WEB-INF/pages/success.jsp");//重定向这样写访问不到
response.getWriter().print("hello2");
return;
}
//返回ModelAndView
@RequestMapping("/sayHello3")
public ModelAndView sayHello3(){
System.out.println("hello3...");
ModelAndView modelAndView=new ModelAndView();
modelAndView.addObject("msg","用户名或密码已经存在");
modelAndView.setViewName("success");
return modelAndView;
}
//返回Model
@RequestMapping("/sayHello7")
public String sayHello7(Model model){
System.out.println("hello7...");
model.addAttribute("msg","用户名或密码已经存在");
return "success";
}
//请求转发,不走视图解析器了
@RequestMapping("/sayHello4")
public String sayHello4(){
System.out.println("hello4");
return "forward:/WEB-INF/pages/success.jsp";
}
//重定向，不走视图解析器了，重定向不可以是隐私目录
@RequestMapping("/sayHello5")
public String sayHello5(){
System.out.println("hello5");
//return "redirect:http://www.itheima.com";
return "redirect:/page/suc.jsp";
}
/*
* 异步的数据交互
* @ResponseBody这个注解要被扫描到，所以要在spring-mvc.xml中配置<mvc:annotation-driven />
* */
@RequestMapping("/sayHello6")
public User sayHello6(@RequestBody User user){
System.out.println(user);
user.setUsername("hello");
user.setAge(40);
return user;
}
}
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